Efficiency of AKD sizing in mixed hardwood-softwood furnishes

Increasing the softwood fraction in a furnish that is chiefly hardwood decr eases final sizing. Some paper producers report similar observations. We su ggest that softwood fines are responsible for this decrease in sizing effic iency. They have a higher surface area due to their slender nature, compare d with stockier hardwood primary fines. In laboratory trials, we evaluated the role of fines. Handsheets made with fibres only (all fines removed) sho wed no effect on sizing when the softwood fraction increased. Generated sec ondary fines (either hardwood or softwood) decreased the sizing more than t he primary hardwood fines alone.